Earth's Internal Structure PDF

Earth’s Internal Structure Date Created @September 10, 2024 4:22 PM Links B_209_02_Earth internal structure.ppt Earth as a Planet: Earth was formed about 4.6 Billion years ago along with other planets that were born from the Nebula Theory. In the early forma...

Earth’s Internal Structure Date Created @September 10, 2024 4:22 PM Links B_209_02_Earth internal structure.ppt Earth as a Planet: Earth was formed about 4.6 Billion years ago along with other planets that were born from the Nebula Theory. In the early formation stage of Earth, it was referred as Proto-Earth which mostly contained of molten-matter, extreme hot temperature and gradual increase in size caused by the process of accretion- where smaller celestial bodies and cosmic dust collide and merges with each other. Planets such as Jupiter, Saturn, Uranus, Neptune all share commonality of gaseous planets, whereas planets such as Mercury, Venus, Earth, Mars are all terrestrial planets, while Earth is the biggest planet of them all. Earth’s shape is best described as geoid and is one the largest heterogeneous structural planet with a diameter of more than 12,000 KM. Direct Observation on Earth’s Interior: Mining galleries which are used to mine ores such as iron and coal can rarely dig more than 2,500 meters into the Earth. On the other hand, wells that are used to extract oil and water can dig between 1000-3000 meters while only few of them can dig up to 10 km. The drills are used to dig underneath Earth can only dig up to certain depth and must be stopped due to extreme high temperatures which can cause damage to the machines and making them inoperable. Seismic Investigation : Seismic Investigation is an artificial method used to study the Earth’s interior. It studies the waves caused by earthquakes, or artificial waves such as controlled blasts. In this method, the seismic waves travels through the Earth’s interior and the wave’s behaviour is impacted by the chemical and environmental composition of the rocks and fluids they encounter. The layers are bodies of rocks are heterogenous and dynamic, due to contrast physical properties between rock layers boundaries illustrating about their diverse nature and not being permanent. Diagram Reflection (return): refers to the return of waves to the surface due to the contact between boundaries of contrast properties. The returned waves are received by geophones or hydrophones, which studies the depth and shape of subsurface structures by measuring the time it takes for the waves to return to the surface. Refraction (bend): refers to the bending of waves as they pass through different and various types of rock boundaries, for such phenomenon to occur the speed of the waves at which it passes through the layers, as well the angle of waves resulting in their alteration must all be considered. Snell’s Law: it describes the connection between wave refraction and incidence angle when moving between layers with various seismic travel speeds. In essence, Natural phenomenas such as earthquakes, volcano eruptions, tsunamis can produce an incredible amount of energy discharge which can result the propagation of seismic throughout the whole Earth. In contrast, artificial energy discharge are relatively weak and less impactful as those seismic do not travel throughout the Earth. Elements of an Earthquake; The origin of the earthquake inside the Earth is known as Hypocenter, while the impacted area right above the Hypocenter is known as Epicentre. Hypocenters can be shallow as 100km into the Earth or deep as ranging from 600-700km. Diagram Seismic Waves (Video): There are two types of Seismic Waves and they both have sub-categories of their own kind; Body Waves: These waves travel through the whole earth and they propagates from the hypocenter. Body waves can travel throughout the Earth as the name suggests “body”. In specific, a part of body waves can even move into the core while, conversely, another part can reach out to the surface. There are two types of body waves; Primary Waves (P-waves): They are the fastest waves and are the first waves to be recorded when an earthquake occurs. These waves can travel through both liquid and solid environments because they compress (crush) and release the rocks as they propagate (advance and multiply). They propagate in a back & forth manner. Secondary/Shear Waves (S-waves): They are second in place followed by P-waves to be recorded. These waves can only travel through solid media due to the their reliance on material’s properties to propagate. They propagate in an up & down motion. Surface Waves: These waves are followed by both P and S waves and are much slower than body waves however, they have a longer duration and larger area of impact, thus make it extremely dangerous from human infrastructure. They usually impact the surface of the Earth, as the name suggests “surface”. There are two types of surface waves; L-Waves (Horizontal): These waves propagate like a snake, it moves the surface from side to side, perpendicular to its travel direction. They are the fastest amongst the surface waves. They put a hard time for human infrastructure to stay stable. R-Waves (Vertical & Elliptical): These waves propagate like ocean wave/tides, it moves the surface in a elliptical (clock) manner. They have the longest duration and spread out the most, slowest out of seismic waves and thus has the potential of demolishing human infrastructure. Chemical Composition: Earth’s interior is divided into three categories, which consists of; Core: The core is mainly composed of iron and nickel, with iron being the most dominant element and nickel being the subdominant element in the core. Mantle: The mantle is mostly composed of Silicate- composed of tightly packed silicone and oxygen ions. Mantle represents around 80% of Earth’s volume with its silicate being the most common mineral group on Earth. The border between mantle and core is known as Guttenberg discontinuity. Silicate: Crust: The crust is the thinnest layer of the Earth and is also silicate-dominated. Its thickness and thinness varies because its thin under the oceans and thick under the continents. In specific, the crust under ocean is mostly composed of iron and magnesium, whereas, the continent’s crust contains light metals, such as aluminum, sodium, potassium with all mainly composed of oxygen, sulphur and carbon. The borderline between mantle and crust is known as, Mohorovichich discontinuity. Diagram: Physical Properties: Earth’s rock layers also varies as it reaches deeper to the core. Therefore, the physical properties of Earth are divided into five categories which includes; Lithosphere: It is the outermost layer of the Earth which includes the crust and uppermost part of the mantle. This layer is in a solid and rigid state and has an average thickness of around 100 km, while ranging between 200-250 km of thickness beneath the continents. It is subdivided into number of slabs, which permanently change their position with respect to lithosphere plates. There are sever major lithospheric plates on Earth; North American Plate Eurasian Plate African Plate South American Plate Australian-Indian Plate Antarctic Plate, and Pacific Plate Diagram: Amongst all the major lithospheric plates, only the Pacific plate is solely consistent of Oceanic crust, whereas all the other plates includes continental mass in them. Asthenosphere: It is situated under the Lithosphere layer and is also known as “upper mantle”, it’s upper part is plastic and they provide foundation to the Lithospheric plates dynamics via convection current in its mass. This layer’s state can be described as soft plastic, therefore can be considered as weak. The rocks situated in this layer moves very slowly. This layer has a depth of around 660 km till its lowest boundary. Mesosphere: This layer is also known as “lower mantle”. The depth of this layer stretches between 660km and 2900km. Despite the presence higher density in this layer, the rocks are still capable slow movements, due to the radiation produced by the core underneath the layer. Outer Core: It is located right below the Guttenberg discontinuity, and stretches approximately between 2900km and 5170km in depth. This layer is in a liquid state, due to the high temperatures of the iron-nickel alloy in its composition. At the core/mantle border, there is a continuous and immense heat transfer from the outer core to the mesosphere. It is a struggle to study about the Outer core because the S waves cannot travel through liquid media. Inner Core: It is resting right in the centre of the Earth, mostly composed of heavy metals such as iron and nickel. Due to the great amount of pressure created by the rocks above this layer, thus, iron and nickel composition results in solid formation of Inner Core upon contact with P-waves. The inner core rotates independently of the earth as a whole. Diagram: Earth is the only planet in our Solar System with cores differentiated into two components.